How Do Lawyers Use Interrogatories?

I am involved in a lawsuit and I had to answer interrogatories.  How do lawyers use interrogatories at trial?

Interrogatories are written questions sent from one party in a lawsuit to an opposing party about issues related to the lawsuit.  For example, in a lawsuit arising from a motor vehicle collision, each driver may send interrogatories to the other ask for driving histories, including whether the opposing driver has ever received a driving citation. The party responding to interrogatories must sign a statement swearing or affirming that the responses to the interrogatories are true.

How are answers used at trial?   Assume for example that you were served with an interrogatory that asked if you were aware of any witness to the car wreck involved in the case.  Assume that you said in answer to the interrogatory that  you were not aware of any witnesses, but then attempted to call an eyewitness at trial.  Unless the opposing party had knowledge of the eyewitness by some other means, the trial judge may well exclude the eyewitness from testifying at trial because you did not include the name and address of the eyewitness in your interrogatory answers.  

There are many other examples.  For instance, if you are asked and fail to disclose a prior criminal conviction, the fact that you did not tell the truth in answering interrogatories can be used at trial.

Interrogatories are an important part of the civil litigation process.  Complete, truthful responses to interrogatories is very important.